Coffee brewing consists essentially of exposing ground, roasted coffee beans to water in order to extract water-soluble compounds from the beans. After extraction, the coffee-infused water is typically filtered to separate the spent beans from the water. Various ways to brew coffee have been developed, including pour-over methods, where water is gradually passed through a bed of ground coffee before passing through a filter and being collected into a holding vessel, and immersion methods, where the coffee and water are held together for the entire duration of the brewing process before separating the water from the spent grounds.
One example of an immersion brewing device is a siphon brewer (also referred to as a vacuum brewer). A siphon brewing device consists of an upper and a lower chamber with a siphon tube connecting the chambers. To use the siphon brewer, the lower chamber is filled with a volume of water and the upper chamber is filled with a volume of ground, roasted coffee beans. A filter prevents the ground coffee from entering the lower chamber. Heat is applied to the lower chamber, resulting in increased water vapor pressure in the lower chamber forcing the water through the siphon tube and into the upper chamber, where it comes into contact with the ground coffee. By continuing to apply heat to the lower chamber, the pressure in the lower chamber remains sufficient to keep the water in the upper chamber while the water is infused with the ground coffee. Once the desired brewing time has elapsed, the heat is removed from the lower chamber, thereby reducing pressure in the lower chamber and drawing the water, now infused with the ground coffee, back into the lower chamber to be served.